As disclosed in U.S. Pat. No. 4,293,915, issued Oct. 6, 1981, entitled "Programmable Electronic Real-Time Load Controller", Carpenter et al., and assigned to the assignee of the present invention, a programmable electronic real-time load controller includes: a plurality of load control circuits, each being adapted to be interconnected with an electrical load circuit or "load"; a hardware clock; and, a programmed data processor for responding to real-time information from the hardware clock to effect control of the energization state of each load in accordance with a time schedule that has been entered by a user into the data processor. The user is permitted to flexibly program the time schedule by selecting, in advance, a number of control events and associated event times for each of the plurality of loads and for each of the plurality of days in a week. Each selected control event either causes the load to be turned on, to be turned off, or to be duty-cycled, from a time in real-time corresponding to the associated event time to a time in real-time corresponding to a subsequent event time. Accordingly, the "on time" of each load is conformed to the periods during which energization of the load is required so as to limit energy consumption at the facility at which the loads are located.
Although the real-time control effected by such a load controller provides acceptable operation under most circumstances, there are certain situations in which strict adherence to a time schedule has certain disadvantages. These situations include those in which environmental conditions external to the facility change in an unexpected and significant manner.
For example, a particular heating or cooling load may be programmed off under real-time control during a certain period of time, e.g., during times when the facility is not being used for normal business purposes, and may be programmed to be on at a certain time so as to bring the facility to a desired inside temperature at the start of the next business day. If the outdoor temperature sharply drops or rises during the time that the heating or cooling load is programmed off, the heating or cooling load will not, by adhering to the time schedule, be able to bring the indoor temperature of the facility to a desired level at the start of occupancy.
As another example, the programming off of a heating or cooling load during night hours or during other periods of nonoccupancy may result in the indoor temperature at the facility falling or rising to a level during the period of nonoccupancy that is capable of causing damage to equipment or material within the facility, that is, perishable materials may spoil or pipes may freeze.
As yet another example, duty-cycle control of a heating or a cooling load by the load controller may present problems on an especially cold or hot day, inasmuch as the reduced capacity of the heating or cooling load due to duty-cycling may be such as to make the heating or cooling load unable to maintain a desired temperature within the facility.
It is therefore an object of this invention to provide an apparatus that permits the real-time control implemented by a programmable electronic real-time load controller to be modified in accordance with changing environmental conditions.
It is another object of this invention to provide such an apparatus which causes the controller to implement an advance start feature in which the time in real-time that a selected load is turned on or duty-cycled is advanced in relation to the amount by which outdoor temperature deviates from a predetermined reference temperature.
It is yet another object of this invention to provide such an apparatus which causes the controller to implement a night setback feature in which a selected load that is programmed off by real-time control is turned on as indoor temperature at the facility deviates from a predetermined reference temperature.
It is still another object of this invention to provide such an apparatus which causes the controller to implement a duty-cycle shift feature in which the on-time of any selected load being duty-cycled is increased in relation to the amount by which indoor temperature at the facility deviates from a predetermined reference temperature.
It is a further object of this invention to provide such an apparatus which permits the user to select or de-select any given load for such advance start, night setback or duty-cycle shift features.
It is yet a further object of this invention to provide such an apparatus which senses the indoor temperatures in a plurality of zones at the facility, and which uses the sensed temperature for a particular zone to cause the controller to modify the real-time control provided for those loads associated with such zone.
It is still a further object of this invention to provide such an apparatus which can be implemented in an easy and inexpensive manner by the use of readily available, integrated circuit, microprocessor components which are compatible with and which function under control of the data processor within the controller.